High performance, high bandgap, lattice-mismatched, photovoltaic cells (10), both transparent and non-transparent to sub-bandgap light, are provided as devices for use alone or in combination with other cells in split spectrum apparatus or other applications.
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3. A photovoltaic converter comprising:
a photovoltaic cell comprising gainp having a bandgap greater than about 1.9 eV, wherein the photovoltaic cell has a junction and is lattice-mismatched to a gaas parent substrate; and
a graded layer positioned between the parent substrate and the photovoltaic cell, wherein:
the graded layer comprises gaas1-xPx, and “x” increases in discrete incremental steps from a first value in a first portion closest to the parent substrate to a second value in a second portion closest to the photovoltaic cell until the proportions of As and P are such that the gaas1-xPx in the second portion has a lattice constant that matches a relaxed lattice constant of the photovoltaic cell,
the graded layer comprises 6 to 10 steps of gaas1-xPx,
each step is between about 1.0 μm and about 2.2 μm thick,
the P content increases and the As content correspondingly decreases from the first portion to the second portion by about 4 percent to about 6 percent per step, and
a last step in the second portion comprises between about 30 percent and 44 about percent P.
1. A photovoltaic converter comprising:
a photovoltaic cell comprising gainp having a bandgap greater than about 1.9 eV, wherein the photovoltaic cell has a junction and is lattice-mismatched to a parent substrate; and
a graded layer positioned between the parent substrate and the photovoltaic cell, wherein:
the parent substrate comprises gaas,
the graded layer has a lattice constant that changes from a first lattice constant in a first portion closest to the parent substrate to a second lattice constant in a second portion closest to the photovoltaic cell, such that the second lattice constant matches a relaxed lattice constant of the photovoltaic cell,
the photovoltaic cell includes an emitter on a front side of the junction and a base on a back side of the junction, and
the photovoltaic converter further comprises: (i) a double heterostructure comprising a back surface confinement layer on the base and a passivation/window layer on the emitter; (ii) a front contact layer comprising doped GaAsP between a metal grid and the passivation/window layer; (iii) an anti-reflection coating on the passivation/window layer between contacts of the front contact layer; and (iv) a back contact layer comprising doped GaAsP on the back surface confinement layer.
5. A photovoltaic converter comprising:
a photovoltaic cell comprising gainp having a bandgap greater than about 1.9 eV, wherein the photovoltaic cell has a junction and is lattice-mismatched to a gaas parent substrate; and
a graded layer positioned between the parent substrate and the photovoltaic cell, wherein:
the graded layer comprises gaas1-xPx, and “x” increases from a first value in a first portion closest to the parent substrate to a second value in a second portion closest to the photovoltaic cell until the proportions of As and P are such that the gaas1-xPx in the second portion has a lattice constant that matches a relaxed lattice constant of the photovoltaic cell,
the photovoltaic cell includes an emitter on a front side of the junction and a base on a back side of the junction, and
the photovoltaic converter further comprises: (i) a double heterostructure comprising a back surface confinement layer on the base and a passivation/window layer on the emitter; (ii) a front contact layer comprising doped GaAsP between a metal grid and the passivation/window layer; (iii) an anti-reflection coating on the passivation/window layer between contacts of the front contact layer; and (iv) a back contact layer comprising doped GaAsP on the back surface confinement layer.
2. The photovoltaic converter of
4. The photovoltaic converter of
the photovoltaic cell includes a base on a back side of the junction and an emitter on a front side of the junction, and
the photovoltaic converter further comprises: (i) a double heterostructure comprising a back surface confinement layer between the graded layer and the base, and a passivation/window layer on the emitter; (ii) a contact layer comprising doped GaAsP between a metal grid and the passivation/window layer; (iii) an anti-reflection coating on the passivation/window layer between contacts of the contact layer; and (iv) an electrically conductive back contact on a back side of the parent substrate.
6. The photovoltaic converter of
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The present application is a divisional of U.S. application Ser. No. 12/992,871, filed on Feb. 7, 2011, which is a national phase entry of PCT Application No. PCT/US09/32480, filed on Jan 29, 2009, which is a continuation-in-part of U.S. application Ser. No. 12/121,463, filed on May 15, 2008, the entire disclosures of which are hereby incorporated herein by reference.
The United States Government has rights in this invention under Contract No. DE-AC36-08GO28308 between the United States Department of Energy and the Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory.
Sunlight is comprised of a broad range or band of solar radiation in a spectrum spanning short wavelength, high energy, ultra-violet light, through mid-wavelength, visible and near infra-red light, and extending into longer wavelength, lower energy infra-red light. Various semiconductor materials have small enough gaps, called bandgaps, between their valence and conduction energy bands that some level of solar radiation energy will cause electrons in their valence energy bands to transition or jump the bandgap from the valence band to the conduction band, where they can become part of the creation of an electric field and electric current when the semiconductor materials are processed and assembled in a manner that enables such solar energy to electric energy conversion. The size of the bandgap determines how much solar energy is necessary to cause the electrons to transition from the valence band to the conduction band, and semiconductor materials exist or can be made with bandgaps to absorb and convert solar energy from any part of the solar spectrum to electric energy. However, each semiconductor material with its bandgap only absorbs and converts
solar energy to electric energy efficiently in a narrow photon energy range that includes and extends slightly higher than its bandgap energy. If the photon energy in the solar radiation is lower than the bandgap, it will not be absorbed and converted to electric energy in that semiconductor material, but will instead continue to be transmitted through the semiconductor material much as light is transmitted through glass. In other words, semiconductor materials are transparent to solar radiation or light with photon energy less than the bandgap energy, and, except for minor absorption losses that create heat, such lower energy solar radiation will pass through such semiconductor materials and not be converted to electric energy. On the other hand, if the photon energy in the solar radiation is very much higher than the bandgap energy of the semiconductor material, it will be absorbed and cause the electrons to jump the bandgap, thus convert some of such energy to electric energy, but the excess energy over the amount needed for the electrons to jump the bandgap will be thermalized and lost in heat dissipation instead of converted to electric energy. Consequently, for efficient conversion of solar energy from the entire solar radiation spectrum to electric energy, multiple bandgaps distributed throughout the solar spectrum may be needed.
The challenge to implement semiconductor photovoltaic converters with multiple bandgaps distributed throughout the broad solar spectrum has been addressed in a number of ways, including, for example, stacking a plurality of single bandgap photovoltaic converters one on top of another so that light with sub-bandgap energy, i.e., photon energy less than the bandgap of a higher bandgap photovoltaic converter, will pass through that converter to the next lower bandgap converter and, if not absorbed there, perhaps to one or more additional, even lower bandgap converters, until it either gets to a semiconductor material with a low enough bandgap that it will be absorbed and converted to electric energy or gets transmitted out of the system. Another approach has been to include a plurality of subcells with different bandgaps in monolithic, multi-bandgap, tandem, photovoltaic converter devices. Still another approach has been to split the solar spectrum into two or more energy bands and direct each band to a different semiconductor cell with an appropriate bandgap for the energy level of the band that is directed to it.
All of these and other approaches have their advantages and disadvantages. For example, the individual, single bandgap photovoltaic converter cells with different bandgaps stacked together is relatively simple, but reflectance of anti-reflection coatings to prevent reflection of the incident solar radiation is inconsistent and not highly efficient for all wavelengths of light in the solar spectrum, so it is difficult to prevent losses due to reflection at the front face of the top cell, and there are a lot of energy losses associated with multiple surfaces and interfaces and with sub-bandgap absorption, and the like. Monolithic, multi-bandgap, tandem, photovoltaic converters eliminate some surfaces and interfaces, but they have similar front surface and anti-reflection coating issues, lattice matching and mismatching of semiconductor materials imposes constraints on semiconductor materials and bandgaps, and they are more difficult and expensive to make. Split spectrum schemes have the advantage of not having to deal with anti-reflection coatings for the entire solar spectrum, but disadvantages include more complexity with more parts, and more interfaces that generally result in more energy losses. The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
The following summary, embodiments, and aspects thereof are described and illustrated in conjunction with systems, tools, and methods which are meant to be examples and illustrative, not limiting or exclusive in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.
High performance photovoltaic converters for converting high energy solar radiation or radiation from other sources to electric energy are provided as stand-alone cell devices for use alone or in combination with other cells in a split spectrum apparatus or other applications. The example embodiments are directed to solar cells comprising group III-V semiconductor materials, for example, but not for limitation, GaInP alloys with bandgaps above 1.9 eV, which is about as high as group III-V alloys lattice-matched to GaAs or Ge substrates can be without resorting to the inclusion of some Al, although the methods and techniques can also be used for other devices and with other materials. In addition to these example aspects and embodiments described above and hereafter, further aspects, embodiments and implementations will become apparent by reference to the drawings and by study and understanding of the following descriptions and explanations.
The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate some, but not the only or exclusive, example embodiments and/or features. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.
In the drawings:
For an overview of several example features, process stages, and principles, an example high performance, high bandgap, lattice-mismatched, photovoltaic converter 10 is shown in
In this description, the terms front and back in relation to orientation of the converter device and components of it refer to the direction that the light propagates through the device. Essentially, the incident light enters the cell on the front of the cell and propagates through the cell and related layers toward the back. Top is sometimes used interchangeably with front, and bottom is sometimes used interchangeably with back. The terms inverted or non-inverted refer to growth sequence or direction. The conventional practice of growing photovoltaic cells on substrates is and has been to grow the base portion, i.e., the back, of the cell first, and then growing the front (e.g., emitter portion) second, so that the back of the cell is set on the substrate and the front of the cell is over the base and exposed to the incident light. That conventional cell growth configuration, i.e., back or base first, followed by front or emitter second, is called non-inverted or upright. Cell configurations grown on a substrate in the opposite sequence or direction, i.e., front or emitter first, followed by back or base second, is called inverted. Cells that have their parent substrate removed are called ultra-thin cells. Also, the diagrams used or shown in the drawings are not drawn true to scale or in correct proportional relationships, because of the impracticality of illustrating nanometer sized, thin film layers and structures, but they are understandable by persons skilled in the art.
The example photovoltaic converter 10 shown in
In this example photovoltaic converter 10, GaInP is used for the cell 12, because it can be formulated to have a direct bandgap in the range between about 1.9 eV to 2.2 eV, as indicated by the GaInP bandgap curve 30 in
One of the challenges in fabricating a 2.1 eV GaInP solar cell is that there is no readily available lattice-matched substrate on which to grow the crystalline GaInP cell. As shown by the line 32 in
Consequently, a method for fabricating the example GaInP cell shown in
Referring now primarily to
After the growth of the graded layers 36, an etch-stop layer 48 of the same lattice constant as the target GaInP cell 12 is grown on the buffer layer 38 of the graded layers 36, followed by a highly doped front contact layer 50 of GaAsP and a thin passivation/window layer 43 of AlInP doped with the same dopant type as will be used for the emitter 44 of the cell 12 (e.g., sulfur dopant for an n-type GaInP emitter), both of which are also formulated to have the same lattice constant as the target cell 12. As mentioned above, there are several etching steps in this process, and such etching can utilize the different chemical characteristics of GaInP and GaAsP to implement selective etching techniques to accomplish the fabrication of the photovoltaic converter device 10. Therefore, in this example, as mentioned above, GaAs1-xPx is used for the graded layers 36, and GaInP is used for the etch-stop layer 48 to set the materials up for selective etching, as will be explained in more detail below.
A GaInP emitter 44 and GaInP base 46 with appropriate doping to form either a n/p or a p/n junction 42 are grown on the passivation/window layer 43 to form the cell 12. Persons skilled in the art know how to dope GaInP to form a cell, so it is not necessary to describe such doping materials, concentrations, and procedures in detail here. Suffice it to say that an example dopant for n-type GaInP material may be sulfur, and an example dopant for p-type GaInP material may be zinc. The emitter 44 is grown first, before the base 46, because, when the epitaxial structure is complete, it will be mounted on a handle 20 (
After the epitaxial growth stage described above, a metal (preferably, but not necessarily, gold or the like) bottom or back grid 54 is electroplated to the back contact layer 52. The GaAsP back contact layer 52 is then etched away between the grids 54, for example, with phosphoric acid and hydrogen peroxide, as shown in
The back or epilayer side of the device is bonded to the transparent handle 20, as shown in
Once the structure is bonded to the transparent handle 20, as shown in
After the parent substrate 40 and graded layers 36 are removed, as explained above, the GaInP etch-stop layer 48 is also removed, for example, but not for limitation, with hydrochloric acid. Removal of the etch-stop layer 48 leaves the highly doped GaAsP contact layer 50 exposed, as shown in
A metal (e.g., gold or the like) top or front contact grid 60 is then electro-plated to the exposed GaAsP contact layer 50, as shown in
Since the GaAsP front contact layer 50 absorbs some of the incident radiation R before it reaches the cell 12, it is etched out of the area between the gold grid lines 60, as shown in
The final structure, as shown in
As mentioned above, this converter structure and method of fabrication can also be done with a GaInP cell grown on a Ge parent substrate, but the specific etchants used to remove the parent substrate are different.
While the example transparent, ultra-thin, single cell, high bandgap, lattice-mismatched photoelectric converter 10 described above is very high performance and very transparent to sub-bandgap light, there can be problems in embodiments that have very thin emitter layers. Often the emitter of a cell is very thin and heavily doped. When the cell 12 structure is grown inverted, i.e., the emitter 44 first and then the base 46, as described above, the emitter layer 44 may be subjected to a lengthy period of elevated temperature during the subsequent growth of the much thicker base 46. With the temperature high for such an extended period, the dopants may diffuse away from the emitter 44 and into the base 46, which can cause problems, including pushing the junction 42 deeper into the cell 12 than desired. Such a deep junction may, for example, reduce the blue response of the cell 12, because shorter wavelengths are absorbed near the front face of the cell.
To address that problem, an alternate embodiment transparent, ultra-thin, single cell, high bandgap, lattice mis-matched, photovoltaic converter 70 is illustrated diagrammatically in
This example transparent, ultra-thin, photovoltaic converter 80 is made somewhat similar to the transparent, ultra-thin, photovoltaic converter 10 described above, but with several differences, including the growth of the base 72 before the emitter 74. As shown in
After the epitaxial growth stage of the fabrication is complete, a metal (e.g., gold or the like) grid 92 is placed on the GaAsP contact layer 88, e.g., by electro-plating or other process known to persons skilled in the art. Then the GaAsP contact layer 88 is etched away between the grid lines 92, as explained above for the photovoltaic converter 10, leaving only GaAsP contacts 88′ between the passivation/window layer 82 and the gold contacts 92, as shown in
The top or front of the finished active structure shown in
Since the cell structure is grown upright with the thick GaInP base 72 grown first, before the much thinner GaInP emitter 74, the emitter 74 is not exposed to high growth temperature levels for nearly as long the process described above for the photovoltaic converter 10, and the resulting junction 73 is more shallow and robust, which is an advantage for more efficient solar energy to electric energy conversion. However, there is a trade-off. The entire spectrum of solar radiation S has to propagate through the transparent handle 80 and epoxy bonding agent 96 to reach the cell 71, as illustrated in
One way to mitigate this problem is to grow the cell 71 and accompanying layers upright in the same manner as described above for the photovoltaic converter embodiment 70, e.g., as shown in
After the device is prepared on the interim handle 100 as explained above, the back surface of the device is permanently bonded to a transparent handle 104 with epoxy in a similar manner as shown in
The process of using an interim handle to hold the cell structure in tact while the parent substrate and graded layer are removed and replaced with a transparent permanent handle can also be used to make a transparent converter with a structure like the transparent photovoltaic converter 70 in
As mentioned above, a problem encountered in the example transparent, inverted, high bandgap, photovoltaic converter 10 illustrated in
To improve the short wavelength (e.g., blue) response in a high bandgap, lattice-mismatched cell that is grown inverted, i.e., emitter first followed by the base, in a photovoltaic converter device, a modified cell growth method may be used. For a description of this method, reference is made to the example high bandgap photovoltaic converter 10 shown in
Referring for example, but not for limitation, to
In this method, however, the emitter 44 portion of the GaInP cell 12 is not doped as it is being grown. Instead, some or all of the preceding GaAsP contact layer 50, and optionally the etch-stop layer 48, is doped with the dopant that is needed to form the emitter 44 portion of the GaInP cell 12 (for example, sulfur, selenium, etc., for n-type doping), as indicated by the dopant atoms 120 in
Depending on the particular circumstances and the desired depth of the junction 42 in the cell 12, it may also be advantageous to deposit the emitter dopant atoms 120, e.g., the sulfur, in only a portion of the thickness of the GaAsP contact layer 50. For example, if a very thin emitter 44 and shallow junction 42 are desired, the sulfur 120 may be deposited only in a first part 122 of the thickness of the GaAsP contact layer and leaving the remainder, e.g., portions 124, 126, of the thickness of the GaAsP contact layer 50 without any sulfur. Then, before the sulfur atoms from the first part 122 can reach and diffuse into the GaInP cell 12 material, they first have to migrate through the undoped portion, e.g., 124, 126, of the GaAsP contact layer 50 that is adjacent the GaInP cell 12 material. By the time the dopant atoms 120 from the first part 122 of the GaAsP contact layer 50 diffuse through the undoped other portion(s) 124, 126 and through the thin passivation/window layer 43 to reach the GaInP cell 12 material, most of the base 46 of the cell 12 will have been grown, and there will be only a short time remaining at the elevated MOCVD temperature for the dopant atoms 120 to actually diffuse into the GaInP cell 12 material before the growth of the base 46 and back contact layer 52 are completed and the MOCVD is stopped. Of course stopping the MOCVD allows the temperature to be decreased, which ends for practical purposes the diffusion of the dopant atoms 120 and sets the junction 42 at a very shallow depth with a very thin emitter 44 in the cell 12, which, as explained above, may provide better blue response than thicker emitters and deeper junctions.
On the other hand, if a slightly deeper junction 42 is desired, the dopant atoms 120 can be deposited in more of the GaAsP contact layer, for example in portions 122 and 124 so that the diffusing dopant atoms reach the GaInP cell 12 material quicker, thus having a longer time to diffuse farther into the cell 12. The spatial extent to which the sulfur actually diffuses depends on several factors, including: (1) The actual sulfur concentration in the GaAsP contact layer 50, because the driving physical force for diffusion is the existence of a gradient in concentration and the tendency of a physical system to reach equilibrium; (2) The growth temperature, which relates to the diffusion coefficient constant; and (3) The remaining growth time after the sulfur flow in MOCVD reactants is terminated, i.e., when the cool down occurs, and the steady state is approached asymptotically. In general, the spatial extent or reach of the dopant (e.g., sulfur or the like) diffusion, thus junction 42 depth into the cell 12, will increase with an increase in any of the three factors listed above. Furthermore, the sulfur diffusion may be influenced by the degree to which the layers beneath the GaAsP contact layer 50, i.e., the GaInP etch-stop layer 48 and even the graded layers 36 may or may not also be doped with the same dopant (e.g., sulfur in this example), for the reasons related to the factor (1). Therefore, it may be desirable to also dope the GaInP etch-stop layer 48 and graded layers 36 to inhibit net diffusion of the dopant atoms 120 from the GaAsP contact layer 50 into the GaInP etch-stop layer 48 and graded layers 36 and to drive them instead toward the GaInP cell 12 material. A series of experiments were conducted wherein the explicit doping of the GaAsP contact layer 50 with sulfur atoms 120 was terminated three-thirds, two-thirds, and one-third of the way through the layer 50, i.e., through only the first part or zone 122, through both the first and second parts or zones 122, 124, or through all of the first, second, and third parts or zones 122, 124, 126, as shown in
The high performance, high bandgap, lattice-mismatched, photovoltaic converter examples 10, 70, and 110 described above are all made to be transparent to sub-bandgap light, but there are applications for non-transparent high performance, high bandgap photovoltaic converters, too. For example, but not for limitation, a split-spectrum solar collector system may include optical components that split the high energy, short wavelength light spectrally from the rest of the spectrum and direct it to a specific high bandgap photovoltaic converter. In such a system, no sub-bandgap light is expected to reach the specific high bandgap photovoltaic converter, so there is no need for it to be transparent to sub-bandgap light.
The example non-transparent, high performance, high bandgap, lattice-mismatched, photovoltaic converter 140 shown in
Development of a lattice-matched 2.1 eV solar cell has been attempted before by growing a quaternary alloy of AlGaInP on a GaAs substrate, but the performance of the cell was not excellent. Aluminum is a gettering element that causes the incorporation of oxygen into the material, and, while it may be used without problems in the thin window layers of most cells, as it is in this photovoltaic converter 140 and those example embodiments described above, it leads to a degradation of the bulk material quality in a thicker, base layer of a cell. Therefore, any advantages gained by growing the cell lattice-matched were apparently undone by the inclusion of aluminum in the alloy. Therefore, this high bandgap, 1.9-2.2 eV photovoltaic converter has a ternary GaInP cell with no aluminum and which is lattice-mismatched to the parent substrate.
As mentioned above, a 2.1 eV GaInP alloy has a relaxed lattice constant of 5.597 Å, which is approximately one percent smaller than the 5.653 Å lattice constant of the GaAs substrate 142. This misfit can be overcome by growing a series of step-graded layers of GaAs1-xPx, where the phosphorous content “x” of each successive layer is increased and the in-plane (i.e., growth plane) lattice constant is correspondingly reduced. Again, continuing gradual increase of “x” can also be done, but there are advantages to increasing in steps rather than smooth, continuous increase. Despite the tensile stress on the GaAsP graded layers, the material has been shown to be resilient to cracking. As explained above in relation to a previous example, a seven-step graded layer 144, each stepped layer being 2 μm thick, with the phosphorus content increased by approximately six percent per layer, has been grown so that the composition of the last layer in the grade (sometimes called the buffer layer 145) is approximately 43 percent phosphorus. Under these conditions, the GaInP active layers may be grown relaxed on the buffer layer 145 with a composition of Ga0.65In0.35P, which has a bandgap of about 2.1 eV. While the bulk quality of the active layers is lower than that of lattice-matched GaInP, the structure of the graded layers minimizes the density of threading dislocations that penetrate the active layers such that satisfactory bulk quality say be achieved.
The cell 150 is designed with a 3-4 μm thick base layer 152 and a thin emitter layer 156 about 200-3000 Å thick for good blue response, as discussed above. Both n/p and p/n configurations are possible, using sulfur, for example, as an n-type dopant and zinc, for example, as a p-type dopant. In the n/p configuration, a back surface confinement 146 can be achieved with a p+ zinc dopant spike, while in the p/n configuration a thin layer of sulfur doped (Ga)AlInP may be required. Front surface passivation can be done with a thin layer of AlInP.
During the epitaxial growth stage, a highly doped GaAsP contact layer 160 is grown on the cell 150 after growing the passivation/window layer 158, as describe above for the other example embodiments, and, as also described above, a contact metal grid 162 (e.g. gold, but other metals will work) is electroplated or otherwise deposited on the GaAsP contact layer 160. Then, as also described above, the GaAsP layer 160 is removed by etching, and an anti-reflection coating 264 is applied to the front surface. A back contact 166, which can also serve as a back surface reflector (BSR), is also applied on the back surface of the GaAs substrate 142, which is doped to be a conductor of current from the cell 150 to the back contact 166.
This non-transparent photovoltaic converter 110 may be grown on a GaP substrate, since the substrate and graded layers do not need to be removed for transparency. The graded layers may still be a compositionally graded set of GaAsP layers, e.g., GaAsyP1-y, but in successively increasing, rather than decreasing, lattice constants. It is also possible for the growth of the cell to be on a silicon substrate or a silicon-germanium substrate, but thermal expansion differences can cause difficulties.
As mentioned above, the exact bandgap of the cell 150 is tunable in the range of approximately 1.9 to 2.2 eV. Depending on the choice of bandgap, the number of steps in the graded layer 144 may be adjusted, as well as the phosphorus content per layer. The bulk quality of the active layers may improve as the bandgap is decreased, as the overall mismatch is thereby lessened. Above approximately 2.2 eV, GaInP becomes an indirect bandgap semiconductor, which may need a significantly thicker cell to achieve comparable performance.
While a number of example aspects and implementations have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions, and subcombinations thereof. It is therefore intended that the following appended claims and claims thereafter introduced are interpreted to include all such modifications, permutations, additions, and subcombinations as are within their true spirit and scope.
The words “comprise,” “comprises,” “comprising,” “composed,” “composes,”, “composing,” “include,” “including,” and “includes” when used in this specification, including the claims, are intended to specify the presence of state features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, or groups thereof. Also the words “maximize” and “minimize” as used herein include increasing toward or approaching a maximum and reducing toward or approaching a minimum, respectively, even if not all the way to an absolute possible maximum or to an absolute possible minimum. In this description and the following claims, growing a layer or component on another layer or component may include either: (i) growing it directly on the other layer or component without any intervening layers or components; or (ii) growing it indirectly on the other layer or component after one or more intervening layers or components are grown.
Wanlass, Mark W, Carapella, Jeffrey J, Steiner, Myles A
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
3900868, | |||
4179702, | Mar 09 1978 | Research Triangle Institute | Cascade solar cells |
4214916, | Feb 05 1979 | Thin film photovoltaic converter and method of preparing same | |
4255211, | Dec 31 1979 | Chevron Research Company | Multilayer photovoltaic solar cell with semiconductor layer at shorting junction interface |
4278474, | Mar 25 1980 | The United States of America as represented by the United States | Device for conversion of electromagnetic radiation into electrical current |
4338480, | Dec 29 1980 | Varian Associates, Inc. | Stacked multijunction photovoltaic converters |
4451691, | Feb 26 1982 | Chevron Research Company | Three-terminal ternary III-V multicolor solar cells and process of fabrication |
4575576, | Nov 07 1984 | UNITED STATES OF AMERICA AS REPRESENTED THE ADMINISTRATOR OF THE DEPARTMENT OF ENERGY, THE | Three-junction solar cell |
4575577, | May 27 1983 | Chevron Research Company; CHERVON RESEARCH COMPANY | Ternary III-V multicolor solar cells containing a quaternary window layer and a quaternary transition layer |
4667059, | Oct 22 1985 | Midwest Research Institute | Current and lattice matched tandem solar cell |
4771321, | Aug 29 1984 | Varian Associates, Inc. | High conductance ohmic junction for monolithic semiconductor devices |
4881979, | Aug 29 1984 | VARIAN ASSOCIATES, INC , A CORP OF DE | Junctions for monolithic cascade solar cells and methods |
4963508, | Sep 03 1985 | Daido Tokushuko Kabushiki Kaisha; NAGOYA INSTITUTE OF TECHNOLOGY | Method of making an epitaxial gallium arsenide semiconductor wafer using a strained layer superlattice |
4963949, | Sep 30 1988 | ENERGY, THE UNITED STATES OF AMERICA AS REPRESENTED BY THE DEPARTMENT OF | Substrate structures for InP-based devices |
5009719, | Feb 17 1989 | Mitsubishi Denki Kabushiki Kaisha | Tandem solar cell |
5019177, | Nov 03 1989 | The United States of America as represented by the United States | Monolithic tandem solar cell |
5053083, | May 08 1989 | BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIVERSITY, THE, A CORP OF CA | Bilevel contact solar cells |
5185288, | Aug 26 1988 | Agilent Technologies, Inc | Epitaxial growth method |
5223043, | Feb 11 1991 | Alliance for Sustainable Energy, LLC | Current-matched high-efficiency, multijunction monolithic solar cells |
5261969, | Apr 14 1992 | Boeing Company | Monolithic voltage-matched tandem photovoltaic cell and method for making same |
5322572, | Nov 03 1989 | The United States of America as represented by the United States | Monolithic tandem solar cell |
5322573, | Oct 02 1992 | UNITED STATES OF AMERICA, THE, AS REPRESENTED BY THE ADMINISTRATOR OF NATIONAL AERONAUTICS AND SPACE ADMINISTRATION | InP solar cell with window layer |
5376185, | May 12 1993 | Midwest Research Institute | Single-junction solar cells with the optimum band gap for terrestrial concentrator applications |
5407491, | Apr 08 1993 | UNIVERSITY OF HOUSTON | Tandem solar cell with improved tunnel junction |
5479032, | Jul 21 1994 | Trustees of Princeton University | Multiwavelength infrared focal plane array detector |
5571339, | Apr 17 1995 | OHIO STATE UNIVERSITY, THE; ESSENTIAL RESEARCH, INC | Hydrogen passivated heteroepitaxial III-V photovoltaic devices grown on lattice-mismatched substrates, and process |
5716459, | Dec 13 1995 | Hughes Electronics Corporation | Monolithically integrated solar cell microarray and fabrication method |
5853497, | Dec 12 1996 | Hughes Electronics Corporation | High efficiency multi-junction solar cells |
5865906, | Aug 23 1996 | JX Crystals Inc. | Energy-band-matched infrared emitter for use with low bandgap thermophotovoltaic cells |
5944913, | Nov 26 1997 | National Technology & Engineering Solutions of Sandia, LLC | High-efficiency solar cell and method for fabrication |
6034321, | Mar 24 1998 | Essential Research, Inc. | Dot-junction photovoltaic cells using high-absorption semiconductors |
6107562, | Mar 24 1998 | Matsushita Electric Industrial Co., Ltd. | Semiconductor thin film, method for manufacturing the same, and solar cell using the same |
6150604, | Dec 06 1995 | UNIVERSITY OF HOUSTON | Quantum well thermophotovoltaic energy converter |
6162768, | Jan 16 1990 | Mobil Oil Corporation | Dispersants and dispersant viscosity index improvers from selectively hydrogenated polymers: free radically initiated direct grafting reaction products |
6162987, | Jun 30 1999 | Energy, United States Department of | Monolithic interconnected module with a tunnel junction for enhanced electrical and optical performance |
6180432, | Mar 03 1998 | Interface Studies, Inc. | Fabrication of single absorber layer radiated energy conversion device |
6218607, | May 15 1997 | JX CRYSTALS INC | Compact man-portable thermophotovoltaic battery charger |
6239354, | Oct 09 1998 | Midwest Research Institute | Electrical isolation of component cells in monolithically interconnected modules |
6252287, | May 19 1999 | National Technology & Engineering Solutions of Sandia, LLC | InGaAsN/GaAs heterojunction for multi-junction solar cells |
6255580, | Apr 23 1999 | The Boeing Company | Bilayer passivation structure for photovoltaic cells |
6265653, | Dec 10 1998 | Lawrence Livermore National Security LLC | High voltage photovoltaic power converter |
6281426, | Oct 01 1997 | Alliance for Sustainable Energy, LLC | Multi-junction, monolithic solar cell using low-band-gap materials lattice matched to GaAs or Ge |
6300557, | Oct 09 1998 | Alliance for Sustainable Energy, LLC | Low-bandgap double-heterostructure InAsP/GaInAs photovoltaic converters |
6300558, | Apr 27 1999 | Sharp Kabushiki Kaisha | Lattice matched solar cell and method for manufacturing the same |
6316715, | Mar 15 2000 | The Boeing Company | Multijunction photovoltaic cell with thin 1st (top) subcell and thick 2nd subcell of same or similar semiconductor material |
6340788, | Dec 02 1999 | Hughes Electronics Corporation | Multijunction photovoltaic cells and panels using a silicon or silicon-germanium active substrate cell for space and terrestrial applications |
6420732, | Jun 26 2000 | LUXNET CORPORATION | Light emitting diode of improved current blocking and light extraction structure |
6482672, | Nov 06 1997 | NATIONAL AERONAUTICS AND SPACE ADMINISTRAION, U S GOVERNMENT AS REPRESENTED BY THE ADMINISTRATOR OF THE | Using a critical composition grading technique to deposit InGaAs epitaxial layers on InP substrates |
6660928, | Apr 02 2002 | ESSENTIAL RESEARCH, INC , A CORP OF OHIO | Multi-junction photovoltaic cell |
6680432, | Oct 24 2001 | SOLAERO TECHNOLOGIES CORP | Apparatus and method for optimizing the efficiency of a bypass diode in multijunction solar cells |
6743974, | May 08 2001 | Massachusetts Institute of Technology | Silicon solar cell with germanium backside solar cell |
6815736, | Apr 24 2001 | Alliance for Sustainable Energy, LLC | Isoelectronic co-doping |
6917061, | Jul 20 2001 | MICROLINK DEVICES, INC | AlGaAs or InGaP low turn-on voltage GaAs-based heterojunction bipolar transistor |
6951819, | Dec 05 2002 | Ostendo Technologies, Inc | High efficiency, monolithic multijunction solar cells containing lattice-mismatched materials and methods of forming same |
7095050, | Feb 28 2002 | Alliance for Sustainable Energy, LLC | Voltage-matched, monolithic, multi-band-gap devices |
7141863, | Nov 27 2002 | University of Toledo | Method of making diode structures |
7309832, | Dec 14 2001 | Alliance for Sustainable Energy, LLC | Multi-junction solar cell device |
7488890, | Apr 21 2003 | Sharp Kabushiki Kaisha | Compound solar battery and manufacturing method thereof |
7675077, | Dec 29 2006 | EPISTAR CORPORATION | Light-emitting diode and method for manufacturing the same |
8067687, | May 21 2002 | Alliance for Sustainable Energy, LLC | High-efficiency, monolithic, multi-bandgap, tandem photovoltaic energy converters |
8173891, | May 21 2002 | Alliance for Sustainable Energy, LLC | Monolithic, multi-bandgap, tandem, ultra-thin, strain-counterbalanced, photovoltaic energy converters with optimal subcell bandgaps |
20020062858, | |||
20020144725, | |||
20030015700, | |||
20030160251, | |||
20040166681, | |||
20040206389, | |||
20050150542, | |||
20050274409, | |||
20050274411, | |||
20060112986, | |||
20060144435, | |||
20060162768, | |||
20060185582, | |||
20070151595, | |||
20070277869, | |||
20080149915, | |||
20080200020, | |||
20090078308, | |||
20090229659, | |||
20090288703, | |||
20110041904, | |||
20110048519, | |||
20110048532, | |||
20110056546, | |||
20110056553, | |||
20110083722, | |||
20110186115, | |||
20120104460, | |||
20120204942, | |||
20120252159, | |||
20120305059, | |||
JP11163380, | |||
JP2003347582, | |||
WO3100868, | |||
WO2004017425, | |||
WO2004022820, |
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